The present invention disclosed herein relates to a method for treating a substrate using plasma, and more particularly, to a method for generating hollow cathode plasma and a method for treating a large area substrate using the hollow cathode plasma, in which ashing, cleaning, and etching processes can be performed on a substrate such as a semiconductor wafer or a glass substrate using the plasma.
In general, various processes such as an etching process, an ashing process, and a cleaning process are required in order to manufacture a semiconductor device. Recently, the above-described processes are being performed using plasma.
An inductively coupled plasma source and a remote plasma source are being selectively used as a plasma source.
FIG. 1 is a cross-sectional view of an inductively coupled plasma (ICP) dry etching apparatus. In an ICP method, when a circular or spiral antenna 12 is installed on a chamber 11 and a high frequency power 13 is applied to the antenna 12, a current flows along a coil to generate an electric field around the coil. As a result, an induced electric field is generated inside the chamber 11 due to the electric field, and electrons are accelerated to generate plasma.
According to the ICP method, the plasma may be generated at a very low pressure, and thus, it is a great advantage to etch a fine pattern. In addition, a bias power 14 may be applied to a wafer electrode to very finely adjust an etching rate.
However, it is difficult to control a radical density at a high pressure in the ICP method. Thus, the fine pattern formation process may be performed at only a low pressure.
In recent, as a semiconductor substrate increases in size, it is required to uniformly distribute a process gas on the substrate. However, it is difficult to etch a large area and control plasma at a high pressure in a plasma etching apparatus using an inductively coupled plasma source.
FIG. 2 is a cross-sectional view of a remote plasma ashing apparatus. Referring to FIG. 2, in a remote plasma ashing apparatus, a remote plasma generator 22 is installed in a reaction gas inlet port disposed outside a chamber 21. Due to the remote plasma generator 22, energy is provided to a reaction gas to activate the reaction gas. The activated reaction gas is injected into the chamber 21 through a gas injection tube 23 to perform an ashing process.
CF4, NH3, N2, and O2 gases are mainly used as the reaction gas. Also, it is difficult to treat a large area substrate, and a plasma density is low in the remote plasma ashing apparatus.
In an ashing process, when a photoresist coated on a low dielectric constant (low-K) dielectric of the substrate is removed using the O2 and N2 gases, the low-k dielectric as well as the photoresist is greatly lost.
Also, in case where a high dose ion implanted photoresist disposed on an oxide material is removed using the O2 and N2 gases, a large amount of photoresist residues is generated.
In addition, when the ashing process is performed using the O2 and N2 gases, a metal of the substrate may be easily oxidized. Particularly, it may be extremely vulnerable to oxidation in case where the metal is a copper (Cu).
Since the remote plasma ashing apparatus uses a material such quartz or sappier as the plasma source, it is vulnerable to a hydrogen plasma process.